iMac 5K Retina 27-inch Desktop 4.2GHz Core-i7, 16GB RAM, 1.03TB Fusion - Best Deal in Town Las Vegas
Memory Upgrades for 2017 iMac 27-Inch
Amazon.com: OWC 32GB (2 x 16GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with Mac Mini (Late 2018), 27" and 21.5" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S32P) : Everything Else
Apple iMac 27-inch 2017 5K 4.2GHz Core i7 8RAM 512GB SSD - Very Good Refurbished | eBay
How to upgrade RAM in the (Mid 2017) 5K iMac and save up to ~$900 [Video] - 9to5Mac